best low poly workflow without decimate
Well, another option would be to use limited dissolve in edit mode. What this does is find subdivided faces that are relative to one another, and share the same position (i.e. a subdivided plane), and merge them into a single face. This would make a subdivided face a normal face once again.

Do this by going to edit mode mesh > clean up > limited dissolve. This function has been useful for me, and I hope it will help you!